31 replies so far

In short, yes you can over clamp and weaken the glue joint. Are you allowing them adequate time to dry? TB3 takes 24 hours to cure. Applying glue to both sides of the joint or only one? Under what conditions are the glue joints failing? Wet? Dry? Dishwasher?

What species of woods are you trying to glue up ?How old is the glue and how are you applying it ?How much time do you allow it to dry / cure ? Temperature of room and glue ?Yes , you can squeeze too much glue out of the joints by over-tightening the clamps.If you have to apply that much pressure to bring your boards together , then something else is wrong with your methods.

Over tightening the clamps is likely – but also using too little glue could be an issue. Don’t be a gorilla when you are tightening the clamps and make sure to have a small bead of squeeze out of glue—- then you’ll be sure to have a good joint.

Personally , I haven’t had any troubles with gluing up the Paduak , but have noticed some pieces to be oilier than most others.The Shedua appears to glue well from what I’ve read today.Drying times vary with Temperature and Humidity : )

You can squeeze out too much(or all) of the glue if you apply to much pressure and the joint can fail…..

This is something Ive heard…I don’t know how many times over the last 22 years as the foreman of a large custom stair and railing shop(and many other types of custom mill work).

(just so you know I’m not blowing smoke)I’m speculating a bit and trying to go on the conservative side….but Ive seen… more than…. 200,000 bd/ft of hardwood lumber of all descriptions, mostly domestics, but also a myriad of different imports go through the shop over the years.We go through, on average, about 120 gallons of PVA a month, and many other types of adhesives for various applications.

There must be some weird JU-JU goin on in the shop, because I can honestly say….in those 22 years…I have NEVER ONCE seen a glue joint fail because of over tightening.And lemme tell ya, Ive seen some real clowns go through the shop in those years. Ive seen guys break the ends of pipe clamps off with wrenches…guys bend and break hand clamps tightening them with a screwdriver in the handle. You name it.Ive seen guys(mentioned above) with horrid mill work practices, close up huge gaps with large #’s of clamps and enormous amounts of pressure.It’s all good and fine until the clamps come off. Cracks, splits, catastrophic failures. But always the lumber, never the glue joint.Don’t get me wrong, Ive seen glue joints fail….but it’s always inadequate, improper, and/or nonexistent surface prep, (or wrong choice of adhesive) of the more oily hardwoods.Could too much pressure weaken a joint in some way, shape or form? Possibly…but to such a minimal degree it’s not even worth mentioning.
In my experience, with today’s modern adhesives…it’s a complete myth.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

Can you post a picture of some of the cracks. You can tell when looking at the joint cracks if there is glue residue on there or not.

While it is possible to squeeze out alot of the glue, I wouldnt think this would be causing all of your issues as long as you used enough glue… was there glue squeeze out when u clamped it? enough to make small beads or even to drip or run?

My first thought was that the glue was bad, but you said it wasnt bad. Was the glue of regular consistency? or was it chunky or goupy?

Was the wood straight grained, or was it very wavy, or non linear from front to back? or other wood stresses?

How many days was the wood in your shop before you used it?

Did you sand the joints before you glued them? or did anything to them besides cutting them on a jointer or table saw?

Ive never worked with paduk, but i agree on the oily wood could be an issue.

before you started ripping the woods into strips after it was glued up, could you physically break the joints with your hands?? I would think if they came apart when you ripped them that they would have come apart with the slightest tug.

How straight were your joints when you put them together? Did it require clamping strength to get your joints perfectly tight? or were they all perfectly tight without even using clamps?

Is your sawblade perfectly 90 degrees? If there is a slight angle it could mess up with your bonding possibly.

How long did you let the wood stay in the clamps? I suggest 24hrs. It should be fine after 3 IF your joints were perfect, if you had to clamp your joints closed then 24hrs is a minimum.

Also since your in Canadian land, not sure what the temperature is out there, but if its COLD where you have the boards in their clamps, it will take longer for the glue to dry. Maybe 24hrs, and if its real real realy cold where you are clamping the board, the glue may not even work.

I’m embarrassed to say that I’ve had the same problem w/ my end-grain boards. Maybe I’m doing my first glue-up incorrectly, but I don’t think so. Remember: the smaller the pieces, the shorter the glue line, and the weaker the joint. I often make boards which end up as a series of 3/4” x 3/4” squares.

My advice is to make your second set of cuts very carefully, and HANDLE THEM VERY CAREFULLY until your final glue-up is in place. As I cut each piece on the RAS, I number them and set them on a piece of plywood to give full-length support when I transport them back to the gluing table . Even then, I’ve had individual pieces break (always at the glue line), so I just re-glue them separately so I don’t have to discard any pieces and lose the grain continuity.

grenger, I’ve made a couple of dozen end grain boards and never once had a glue joint fail.

I would NEVER apply glue to just one face for a joint. Never. I try not to have too much squeeze out, but if you’re stingy with the glue, you’re asking for a failed joint. The wood is going to soak up a certain amount of glue. If the dry side of your joint doesn’t get any glue until it touches the glued face, it’s going to soak up some of it. I don’t know who gave out that info, putting glue only on one face, but I believe it’s absolutely wrong.

Now, for being stingy with the glue, if you clamp those suckers as hard as you can, you’re going to squeeze out glue which would have stayed to make a joint. I tighten my clamps until the gaps are closed and I get a little squeeze out. If you never get any squeeze out, I’d say you’re not putting on enough glue.

I’m not a pro and I’ve wasted lots of wood and time, but I’ve never lost an edge grain cutting board because of a failed glue joint. I use Tite Bond, and I’m sold on it.

I am confident that if you apply glue to both faces and don’t overclamp, you will not have such failures.

Jim,Even an 1/8” thick piece of wood, edge grain glued shouldnt come apart from the joint. if its done correctly if you try to break the joint, more than likely the wood will rip elsewhere besides the glue joint. many times the glue joint ends up being stronger than the actual wood.

If you have to handle them carefully, then something is already wrong.

Another thing I thought of when reading your comment on 3/4” strips, is that depending on temperature, you need to not be patient with the gluing process. Get it all glued up and clamped in a quick time. Less than 5 minutes preferably.

Also not talking thickness of the wood, but the width of the wood you use on your first glue up (Which is basically a glued panel/table top) the smaller the width the more pieces you will need to get your desired board size. And the more board pieces you use, the more your joints will show error.

when you do a glue up then say you cut your strips right then you flip them up for endgrain do you cleanup the squeeze out side before you do the next step I usually run mine back through the tablesaw and take a superfine cut to get rid of all the squeezeout before I do my endgrain glueup